Add flags to control nohz and domain isolations from "isolcpus=", inorder to centralize the isolation features to a common interface. Domainisolation remains the default so not to break the existing isolcpusboot paramater behaviour.

Further flags in the future may include 0hz (1hz tick offload) and timers,workqueue, RCU, kthread, watchdog, likely all merged together in acommon flag ("async"?). In any case, this will have to be modifiable bycpusets.